35 Urinary Bladder

STUDYAIMS

At the end of your study, you should be able to:

Describe the course of the pelvic ureters

Outline the gross structure of the bladder

Describe the relations of the bladder

Describe the structure of the male urethra

Describe the structure of the female urethra

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GUIDE

Pelvis and Perineum: Urinary Bladder

[Plate 348, Urinary Bladder: Orientation and Supports]

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[Plate 351, Male and Female Cystourethrograms]

Ureters

Cross pelvic brim at the level of sacroiliac joint, anterior to the bifurcation common iliac arteryto pierce the posterior surface of the bladder Enters the posterolateral surface of the bladder and runs obliquelythrough the bladder wall, creating a flap valve

In males: the ureter passes under the ductus deferens, superior to the seminal vesicles

In women: the ureter descends posterior to the ovaryand into the base of the broad ligament passing under the uterine artery("water under the bridge")

Supplied bybranches of common and internal iliac arteries and uterine artery(inferior vesicle arteryin males) and drained byveins with same names.

Innervated byfibers from adjacent autonomic plexuses

Urinary Bladder

General structure

Lies posterior to pubic bones and pubic symphysis

When emptyis tetrahedron in shape and lies entirelywithin true pelvic cavity; spherical when full and mayreach as high as umbilicus When emptyhas a base (posterior surface) and a superior and two inferolateral surfaces.

Base (posterior surface) of bladder defined internallybytwo ureteric openings at superolateral corners and internal urethral opening inferiorly

Triangular area defined bythese openings is the vesicle trigone Ridge between two urethral openings is the interureteric fold

Neck of bladder is where base and inferolateral sides meet, inferiorly

Anterior angle or apexis site of attachment of urachus-fibrous remnant of fetal allantois, which is seen as the median umbilical ligament on the anterior abdominal wall

Bladder wall is composed of a thick layer of interwoven bundles of smooth muscle running transversely, longitudinally, and obliquelydetrusor muscle

In region of neck, detrusor muscle runs circularlyas involuntaryinternal sphincter Bladder mucosa is thrown into rugae except within trigone, which is smooth

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Relations of the Urinary Bladder

Superior vesicle arteries (branches of internal iliac artery) supplyapexand superior part of bladder

Inferior vesical arteries supplyfundus and neck in males

Vaginal arteries (branches of uterine arteries) supplyfundus and neck in females

Obturator arteries (branches of internal iliac artery) provide arterial twigs

Venous drainage

Vesical venous plexus drains to internal iliac plexus via inferior vesical veins

Communicates with prostatic venous plexus in males and uterovaginal venous plexus in females

Female urethra

Threeto 4-cm long fibromuscular tube, bound to anterior vaginal wall

Extends from internal urethral meatus of bladder to external meatus situated just anterior to the vaginal opening in the vestibule Descends with vagina through urogenital hiatus and pelvic diaphragm and through perineal membrane where it is surrounded byexternal sphincter urethrae

Paraurethral glands, homologs to the prostate, open on either side near external urethral orifice Supplied byinternal pudendal and vaginal arteries

Drained byveins of same name

Innervated bybranches of pudendal nerve via S2-S4 spinal cord segments and afferents run with pelvic splanch

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Male urethra

Twenty-cm fibromuscular tube

Conveys both urine and semen

Extends from internal urethral meatus of bladder to external urethral meatus in glans penis

Divided into three parts: prostatic; membranous and spongyurethra

Comparison of Prostatic, Membranous and Spongy Parts of the Male Urethra

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